1. Field of the Invention
Aspects of the present invention are directed to a method and apparatus for operating logical partitions and, more particularly, to a method and apparatus for operating logical partitions to run in vertical mode.
2. Description of the Background
Recently, as high-end server architectures have been improved in terms of providing faster processing speeds and offering greater storage capacity, numbers of processors used by the servers have increased. As such, the processor “nest” needed to build large machines operating as servers continues to be made of smaller and smaller building blocks.
As these trends have continued, however, certain issues with server architectures have been made apparent. Among these is a tendency for the server to go “off node” to resolve a cache miss during the processing of an application. Here, although work may be scheduled for distribution to a particular local processor and associated cache, L1, the necessary cache line is actually resident in a remote cache, L2. The penalty for going off node to resolve the cache miss is relatively significant and continues to increase. That is, resolving the L1 miss in the remote L2 is expensive in terms of processing time as compared to resolving it in the local cache. Further, while a cache miss with respect to a local cache is expensive to start with, increases in the speed of memory access and the connections to remote memory are not keeping pace with the growth of problems arising from these issues.
Recently, solutions to the issues have been proposed and relate to the introduction of logical partitions (LPARs) and LPAR managers (or, alternately, LPAR hypervisors), which attempt to optimize the allocation of processing resources and storage resources to particular LPARs in accordance with machine topologies. Examples of these attempts include intelligent resource direction and the use of concurrent book repair methods and methods of dispatching work for certain LPARs on the same physical processors. The latter method has been effective, but for the fact that it may lead to delays if the physical processors are previously occupied with work.
Another method relates to operating LPARs “horizontally”. In this method, each LPAR is assigned a share of processing resources while scheduling algorithms evenly spread the LPAR's share among physical processors (or, alternately, logical processors) to which the LPAR has access. While this method may have advantages as long as various LPARs do not have to compete for resources, if the LPARs have to compete for resources, operating LPARs in horizontal mode may be inefficient.